I don’t think the grace period is needed here because the PEP won’t be evaluated solely on where things stand today. We understand the work is ongoing and the current state isn’t the final state (as is true of most things in open source).
While performance goals are something the PEP should definitely address, they’re one piece of the puzzle. Kicking off the community discussion now should actually help shape the PEP rather than the other way around. Having an explicit, public conversation about what people expect from a JIT, in terms of performance targets, interop guarantees, and tooling compatibility, is something we haven’t had in a structured way. The PEP should be an opportunity to surface and settle those expectations.